The electrical P.D. across the integument of some neotenous urodele amphibians

Abstract

1. 1. An electrical P.D. (inside positive) was recorded in vivo across the integument of the neotenous urodeles Amphiuma means, Siren lacertina and Necturus maculosus and this was related to the sodium concentration in the external bathing media. 2. 2. Like in the frog, Rana pipiens, this P.D. in vivo was inhibited when amiloride was placed in the external solutions bathing Amphiuma and Siren but not Necturus. 3. 3. A P.D. and short-circuit current (SCC) was also observed across the skin of Amphiuma and Siren (but not Necturus) in vitro and this was also inhibited by amiloride. In contrast to the responses of the skin of fully metamorphosed amphibians vasotocin did not stimulate the SCC in these neotenous species. 4. 4. Substitution of sulfate for chloride in the external solution in vitro markedly increased the P.D. of frog skin but had no effect on that of Amphiuma or Siren. 5. 5. The results suggest that the exchanges of ions across frog skin are much greater than in the skin of Amphiuma or Siren. A mechanism for active transmural transport of sodium would appear to exist in the skin of these urodeles but the evidence for this in Necturus was equivocal.